Abstract

Four sodium silicate solutions of modulus m = 1.0, 1.2, 1.4 and 1.6 were prepared as activators used in metakaolin-based geopolymer synthesis. The effects of modulus of activator on the mechanical properties and microstructure of the geopolymers were studied by strength test, infrared analysis (IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results showed that the most SiO 4 tetrahedrals were in low poly-degree status when the modulus varied from 1.0 to 1.6. Compressive strength and flexural strength increased with the curing time. The geopolymer of m = 1.2 achieved the highest compressive strength at 28d (74.6MPa) and its flexural strength was 11.2 MPa. The mineral composition of 4 geopolymers was similarly amorphous, and composed of geopolymeric gels and residual raw particles, while the microstructure of the geopolymer of m = 1.2 was the smoothest one.